Energies

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18 pages, 1617 KiB

Open AccessArticle

Life Cycle Assessment of the Use of Phase Change Material in an Evacuated Solar Tube Collector

by Agnieszka Jachura and Robert Sekret

Energies 2021, 14(14), 4146; https://doi.org/10.3390/en14144146 - 09 Jul 2021

Cited by 9 | Viewed by 2191

This paper presents an environmental impact assessment of the entire cycle of existence of the tube-vacuum solar collector prototype. The innovativeness of the solution involved using a phase change material as a heat-storing material, which was placed inside the collector’s tubes-vacuum. The PCM [...] Read more.

This paper presents an environmental impact assessment of the entire cycle of existence of the tube-vacuum solar collector prototype. The innovativeness of the solution involved using a phase change material as a heat-storing material, which was placed inside the collector’s tubes-vacuum. The PCM used in this study was paraffin. The system boundaries contained three phases: production, operation (use phase), and disposal. An ecological life cycle assessment was carried out using the SimaPro software. To compare the environmental impact of heat storage, the amount of heat generated for 15 years, starting from the beginning of a solar installation for preparing domestic hot water for a single-family residential building, was considered the functional unit. Assuming comparable production methods for individual elements of the ETC and waste management scenarios, the reduction in harmful effects on the environment by introducing a PCM that stores heat inside the ETC ranges from 17 to 24%. The performed analyses have also shown that the method itself of manufacturing the materials used for the construction of the solar collector and the choice of the scenario of the disposal of waste during decommissioning the solar collector all play an important role in its environmental assessment. With an increase in the application of the advanced technologies of materials manufacturing and an increase in the amount of waste subjected to recycling, the degree of the solar collector’s environmental impact decreased by 82% compared to its standard manufacture and disposal. Full article

(This article belongs to the Special Issue Heating, Cooling, and Ventilation Systems: Applications and Performance)

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15 pages, 2535 KiB

Open AccessArticle

Passive Cooling Solutions to Improve Thermal Comfort in Polish Dwellings

by Joanna Ferdyn-Grygierek, Krzysztof Grygierek, Anna Gumińska, Piotr Krawiec, Adrianna Oćwieja, Robert Poloczek, Julia Szkarłat, Aleksandra Zawartka, Daria Zobczyńska and Daria Żukowska-Tejsen

Energies 2021, 14(12), 3648; https://doi.org/10.3390/en14123648 - 18 Jun 2021

Cited by 12 | Viewed by 2069

Abstract

The household sector in Poland consumes more than 25% of final energy. At the same time, residents reported dissatisfaction with the thermal conditions during the summer months. This paper details the search for passive and energy-efficient solutions to improve thermal comfort in Polish [...] Read more.

The household sector in Poland consumes more than 25% of final energy. At the same time, residents reported dissatisfaction with the thermal conditions during the summer months. This paper details the search for passive and energy-efficient solutions to improve thermal comfort in Polish dwellings. A five-story, multi-family building was selected for this research. Analyses were conducted in apartments located on the top two floors using EnergyPlus (for thermal calculations) and CONTAM (for air exchange calculations) simulation programs for current and future climatic conditions. The stochastic behavior of people when opening windows and automatically controlled systems supplying external air to the building was considered. Airing the apartments by opening windows increased the heating demand but reduced the number of thermal discomfort hours by over 90%. The degree of airing by opening windows depends on residents opening their windows; therefore, a mechanical supply of external air controlled by both internal and external temperatures was proposed and tested. Full article

(This article belongs to the Special Issue Heating, Cooling, and Ventilation Systems: Applications and Performance)

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18 pages, 4736 KiB

Open AccessArticle

Developing a Cold Accumulator with a Capsule Bed Containing Water as a Phase-Change Material

by Robert Sekret and Przemysław Starzec

Energies 2021, 14(9), 2703; https://doi.org/10.3390/en14092703 - 08 May 2021

Cited by 3 | Viewed by 1812

Abstract

The paper presents the investigation of a prototype cold accumulator using water–ice latent heat for the cold storage process. The concept of the cold accumulator was based on a 200-L-capacity cylindrical storage tank in which spherical capsules filled with water were placed. Beds [...] Read more.

The paper presents the investigation of a prototype cold accumulator using water–ice latent heat for the cold storage process. The concept of the cold accumulator was based on a 200-L-capacity cylindrical storage tank in which spherical capsules filled with water were placed. Beds of polypropylene capsules with diameters of 80 mm, 70 mm, and 60 mm were used in the tests. The cold accumulator operated with a water–air heat pump. Based on the test results, the following parameters were calculated: the cooling capacity, cooling power, energy efficiency of the cold storage, and energy efficiency ratio (EER) of the accumulator. The obtained measurement results were described with mathematical relationships (allowing for measurement error) using criterial numbers and the developed “Research Stand Factor Number” (RSFN) index. It has been found that, for the prototype cold accumulator under investigation, the maximum values of the cooling capacity (17 kWh or 85.3 kWh per cubic meter of the accumulator), energy efficiency (0.99), and EER (4.8) occur for an RSFN of

144 \cdot 10^{- 4}

. The optimal conditions for the operation of the prototype cold accumulator were the closest to laboratory tests conducted for a bed with capsules with a diameter of 70 mm and a mass flow of the water–glycol mixture flowing between the accumulator and the heat pump of 0.084 kg/s. During the tests, no significant problems with the operation of the prototype cold accumulator were found. Full article

(This article belongs to the Special Issue Heating, Cooling, and Ventilation Systems: Applications and Performance)

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16 pages, 6426 KiB

Open AccessArticle

Annual Energy Performance of an Air Handling Unit with a Cross-Flow Heat Exchanger

by Piotr Michalak

Energies 2021, 14(6), 1519; https://doi.org/10.3390/en14061519 - 10 Mar 2021

Cited by 6 | Viewed by 2891

Abstract

Heat recovery from ventilation air is proven technology resulting in significant energy savings in modern buildings. The article presents an energy analysis of an air handling unit with a cross-flow heat exchanger in an office building in Poland. Measurements were taken during one [...] Read more.

Heat recovery from ventilation air is proven technology resulting in significant energy savings in modern buildings. The article presents an energy analysis of an air handling unit with a cross-flow heat exchanger in an office building in Poland. Measurements were taken during one year of operation, from 1 August 15 to 31 July 16, covering both heating and cooling periods. Calculated annual temperature efficiency of heat and cold recovery amounted to 65.2% and 64.6%, respectively, compared to the value of 59.5% quoted by the manufacturer. Monthly efficiency of heat recovery was from 37.6% in August to 68.7% in November, with 63.9% on average compared to 59.5% declared by the manufacturer. Cold recovery was from 63.3% in April to 72.8% in September, with 68.1% annually. Calculated recovered heat and cold amounted 25.6 MWh and 0.26 MWh, respectively. Net energy savings varied from −0.46 kWh/m² in August, when consumption by fans exceeded savings, to 5.60 kWh/m² in January. Full article

(This article belongs to the Special Issue Heating, Cooling, and Ventilation Systems: Applications and Performance)

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21 pages, 3479 KiB

Open AccessArticle

The Energy-Saving Potential of Chilled Ceilings Combined with Personalized Ventilation

by Aleksandra Lipczynska, Jan Kaczmarczyk and Arsen Melikov

Energies 2021, 14(4), 1133; https://doi.org/10.3390/en14041133 - 20 Feb 2021

Cited by 3 | Viewed by 1655

Abstract

The energy consumption of purely convective (i.e., various air volume (VAV) mixing ventilation) and combined radiant and convective HVAC systems (chilled ceiling combined with mixing ventilation—CCMV or personalized ventilation—CCPV) was investigated with multi-variant simulations carried out the IDA Indoor Climate and Energy software. [...] Read more.

The energy consumption of purely convective (i.e., various air volume (VAV) mixing ventilation) and combined radiant and convective HVAC systems (chilled ceiling combined with mixing ventilation—CCMV or personalized ventilation—CCPV) was investigated with multi-variant simulations carried out the IDA Indoor Climate and Energy software. We analyzed three different climates: temperate, hot and humid, and hot and dry. Our results show that the use of CCPV substantially reduced energy consumption compared to the conventional VAV system in hot climates. We also show that increasing the room temperature to 28 °C is an effective energy-saving strategy that can reduce consumption by as much as 40%. In the temperate climate, the VAV system was preferable because it used less energy as it benefited from outdoor air free-cooling. The control strategy of the supply temperature of personalized air had an impact on the energy demand of the HVAC system. The most efficient control strategy of the CCPV system was to increase the room temperature and keep the supply air temperature in the range of 20–22 °C. This approach consumed less energy than VAV or CCMV, and also improved the relative humidity in the hot climate. Full article

(This article belongs to the Special Issue Heating, Cooling, and Ventilation Systems: Applications and Performance)

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18 pages, 2754 KiB

Open AccessArticle

Numerical Analysis of the Energy Consumption of Ventilation Processes in the School Swimming Pool

by Piotr Ciuman and Jan Kaczmarczyk

Energies 2021, 14(4), 1023; https://doi.org/10.3390/en14041023 - 16 Feb 2021

Cited by 5 | Viewed by 3063

Abstract

Ventilation of an indoor swimming pool is a very energy consuming process. This is a result of, among other things the required high value of the ventilation air volume flow rate, calculated on the basis of the moisture gains in the facility. The [...] Read more.

Ventilation of an indoor swimming pool is a very energy consuming process. This is a result of, among other things the required high value of the ventilation air volume flow rate, calculated on the basis of the moisture gains in the facility. The total energy consumption consists of the heat required to heat this air and the electricity needed to transport it. It is possible to reduce the ventilation air volume flow rate by assuming the correct value of specific humidity of the supply and indoor air, but then a deterioration of thermal-moisture conditions in the building can be expected. The aim of this paper was to examine how the reduction of the supply air volume flow rate affects the energy consumption for indoor swimming pool ventilation. It was also checked how this consumption can be reduced by using two-stage heat recovery in the air handling unit. Multi-variant simulations of energy consumption for indoor swimming pool ventilation were carried out using the IDA ICE software for day and night operation of the swimming pool throughout the year. The results of the research proved that reduction of the supply air volume flow rate resulted in the lower energy expenditure on ventilation. The variant with additional local air supply to the lifeguard zone was also analysed, which caused only a slight increase in energy demand for ventilation. Full article

(This article belongs to the Special Issue Heating, Cooling, and Ventilation Systems: Applications and Performance)

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10 pages, 17005 KiB

Open AccessArticle

Viability of Various Sources to Ignite A2L Refrigerants

by Dennis K. Kim and Peter B. Sunderland

Energies 2021, 14(1), 121; https://doi.org/10.3390/en14010121 - 28 Dec 2020

Cited by 1 | Viewed by 2605

Abstract

Environmental considerations are motivating the adoption of low global warming potential refrigerants. Most of these are mildly flammable, i.e., A2L. Their susceptibility to ignition from various ignition sources is poorly understood, particularly for the stoichiometric and quiescent mixtures that are emphasized here. The [...] Read more.

Environmental considerations are motivating the adoption of low global warming potential refrigerants. Most of these are mildly flammable, i.e., A2L. Their susceptibility to ignition from various ignition sources is poorly understood, particularly for the stoichiometric and quiescent mixtures that are emphasized here. The viability of fifteen residential ignition sources to ignite four A2L refrigerants is considered. Tests are performed in a windowed chamber with a volume of 26 L. The refrigerants are R-32 (difluoromethane); R-452B (67% R-32, 26% R-1234yf, and 7% pentafluoroethane); R-1234yf (2,3,3,3-tetrafluoropropene); and R-1234ze (1,3,3,3-tetrafluoropropene). Two types of ignition sources are confirmed here to be viable: a resistively heated wire at 740 °C and open flames. When the refrigerant concentration was increased slowly, candle flames and butane flames extinguished before initiating any large deflagrations. Eleven other sources were not viable: a smoldering cigarette, a butane lighter, friction sparks, a plug and receptacle, a light switch, a hand mixer, a cordless drill, a bread toaster, a hair dryer, a hot plate, and a space heater. The difficulty to ignite these refrigerants in air is attributed to their long quenching distances (up to 25 mm). Under some conditions the refrigerants were observed to act as flame suppressants. Full article

(This article belongs to the Special Issue Heating, Cooling, and Ventilation Systems: Applications and Performance)

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17 pages, 1680 KiB

Open AccessArticle

Impact of Passive Cooling on Thermal Comfort in a Single-Family Building for Current and Future Climate Conditions

by Krzysztof Grygierek and Izabela Sarna

Energies 2020, 13(20), 5332; https://doi.org/10.3390/en13205332 - 13 Oct 2020

Cited by 15 | Viewed by 2060

Abstract

Today, there is a great deal of emphasis on reducing energy use in buildings for both economic and environmental reasons. Investors strongly encourage the insulating of buildings. Buildings without cooling systems can lead to a deterioration in thermal comfort, even in transitional climate [...] Read more.

Today, there is a great deal of emphasis on reducing energy use in buildings for both economic and environmental reasons. Investors strongly encourage the insulating of buildings. Buildings without cooling systems can lead to a deterioration in thermal comfort, even in transitional climate areas. In this article, the effectiveness of natural ventilation in a passive cooling building is analyzed. Two options are considered: cooling with external air supplied to the building by fans, or by opening windows (automatically or by residents). In both cases, fuzzy controllers for the cooling time and supply airflow control are proposed and optimized. The analysis refers to a typical Polish single-family building. Simulations are made with the use of the EnergyPlus program, and the model is validated based on indoor temperature measurement. The calculations were carried out for different climate data: standard and future (warmed) weather data. Research has shown that cooling with external air can effectively improve thermal comfort with a slight increase in heating demand. However, to be able to reach the potential of such a solution, fans should be used. Full article

(This article belongs to the Special Issue Heating, Cooling, and Ventilation Systems: Applications and Performance)

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7 pages, 774 KiB

Open AccessArticle

Analysis of Yearly Effectiveness of a Diaphragm Ground Heat Exchanger Supported by an Ultraviolet Sterilamp

by Sławomir Rabczak and Paweł Kut

Energies 2020, 13(11), 2804; https://doi.org/10.3390/en13112804 - 01 Jun 2020

Cited by 2 | Viewed by 1710

Abstract

Ground heat exchangers supplement ventilation systems and provide notable power gains by heating ventilated air during winter and cooling it in summer. Additionally, they prevent recuperator exchangers from freezing. In atmospheric air, there are many types of contaminants and microorganisms that significantly affect [...] Read more.

Ground heat exchangers supplement ventilation systems and provide notable power gains by heating ventilated air during winter and cooling it in summer. Additionally, they prevent recuperator exchangers from freezing. In atmospheric air, there are many types of contaminants and microorganisms that significantly affect the quality of ventilated air. The air that flows through the system of pipes of the heat exchanger may also become contaminated. In order to remove contamination from ventilated air, ultraviolet radiation may be used. This article presents a concept of using a UV-C (ultraviolet with a wavelength of 200–280 nm) lamp in the air duct in front of the air handling unit connected to the ground heat exchanger. The UV-C lamp, apart from clearing the air, may also decrease operational costs thanks to eliminating contamination that forms bacterial jelly on heat exchanger elements. Full article

(This article belongs to the Special Issue Heating, Cooling, and Ventilation Systems: Applications and Performance)

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